Running Untrusted Code in Node

Transcript

1. 1.

   Running untrusted code in Node in a safe mode while

   handling the lode
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   lode?

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   Dave Wasmer @davewasmer Developer @ Kinvey yep, this slide …

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   Kinvey Backend as a service … and this one.

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   What goes into backend as a service?

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   None
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   Lots o’ stuff • Data storage • User management •

   Twitter, Facebook, G+, LinkedIn • OAuth, LDAP, Active Directory • File storage • don’t forget CDN delivery • Push notifications • Emails • 3rd Party API Integration • Analytics • a whole lot more ..
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   What if CRUD ain’t enough?

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   enter: Business Logic!

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    Run your code on our servers

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    Custom JavaScript execution?!

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    eval(customerCode); // Genius, mirite? NO!

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    The Problem We needed a safe, scalable way to run

    arbitrary (possibly malicious) JavaScript on our servers.
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    Safety • Can’t allow access to: • filesystem • shared

    memory • Kinvey internals • State is evil!
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    Scalablity • Needs to scale horizontally • i.e. spin up

    new instances on-demand • automatically add to resource pool • Optimize for usage • not running huge computations - short, frequent bursts of activity • 2x per API request is possible!
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    Our solution to scalability KCS KCS KCS KBL KBL KBL

    Redis Work Master Child Child Child Child
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    Our solution to scalability KCS KCS KCS KBL KBL KBL

    Redis Work Master Child Child Child Child
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    Our solution to scalability KCS KCS KCS KBL KBL KBL

    Redis Work Master Child Child Child Child
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    Our solution to scalability KCS KCS KCS KBL KBL KBL

    Redis Work Master Child Child Child Child
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    Our solution to scalability Work Master Child Child Child Child

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    Safety Concerns • How to run arbitrary JS code? •

    Three issues • System access (filesystem, network, etc) • Application access (application state, data, etc) • Stupidity / DoS (while (true), forgot to signal async completed)
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    System access • Filesystem • Severely limited or none •

    Network • Partially limited
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    Our solution to system access ! // Setting things up

    ! try { script = vm.createScript(codeAsStr); } catch (e) { // syntax error! } ! sandbox = generateNewSandbox()
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    generateNewSandbox = function(){ ! var sandbox = {}; sandbox.complete =

    function(){ runNextTask(); }; sandbox.whateverYouWant = function(){ ... } return sandbox; ! } Our solution to system access
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    ! // Running the untrusted script try { script.runInNewContext(sandbox) }

    catch (e) { // e will be any immediate (synchronous) // runtime errors } Our solution to system access
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    Application access • Data • Permissions

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    Our solution to application access ! // inside generateNewSandbox() !

    sandbox.db = { find: function(query, callback) { // do db stuff callback(null, result) // <- Careful! }, ...
 }
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    Stupidity / DoS • while (true) {} // single-threaded ftw!

    • function onPreSave(req, res, modules) {
 doSomeAsyncStuff()
 } // kthxbai • function doSomeAsyncStuff() {
 setTimeout(function(){ 
 throw new Error() 
 }, 100000); // muhahaha
 }
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    Our solution to stupidity / DoS Work Master Child Child

    Child Child
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    Our solution to stupidity / DoS Work Master Child Child

    Child Child
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    Our solution to stupidity / DoS ! // For handling

    callback errors process.on(‘uncaughtException’, function(){ // handle it here });
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    Wrap-up